Predictive Value of CT-based Extracellular Volume Fraction in the Preoperative Pathologic Grading of Rectal Adenocarcinoma: A Preliminary Study

Objective: This study aimed to investigate whether the extracellular volume fraction (ECV) determined using enhanced computed tomography (CT) can predict the pathologic grade of rectal adenocarcinoma.Methods: We prospectively analyzed 43 patients with rectal adenocarcinoma confirmed surgically and pathologically and who had undergone preoperative enhanced CT imaging. The plain, arterial, venous, and balance phase values were recorded, and the absolute contrast-enhanced CT differences & UDelta;S1 = HUarterial phase-HUplain scan, & UDelta;S2 = HUvenous phase-HUplain scan, & UDelta;S3 = HUbalance phase-HUplain scan were obtained. The ECV of the primary lesion was calculated by measuring the CT values of the regions of interest in the plain and balance phases. Patients were allocated to either a low-grade or a high-grade group based on the histologic grading standard for colorectal adenocarcinoma (nonspecial type, World Health Organization 2010 standard). The differences in the parameters between the two groups were evaluated for statistical significance. A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic efficiency.Results: The 43 enrolled patients [12 in the high-grade group (27.9%) and 31 in the low-grade group (72.1%)] had an average age of 64.47 years. The arterial phase (P = 0.005) as well as & UDelta;S1 (P = 0.006), & UDelta;S3 (P = 0.021), and ECV (P < 0.001) differed significantly between the high-grade and low-grade groups, with ECV (P < 0.001) and & UDelta;S3 (P = 0.042) being positively correlated with the pathologic grade and arterial phase (P = 0.025) and & UDelta;S1 (P = 0.005) being negatively correlated. The ROC curve demonstrated that the best efficacy in evaluating the pathologic grade of rectal cancer was achieved by ECV, with an area under the curve of 0.892 (95% confidence interval: 0.757-1.000). The diagnostic threshold was 34.42%, sensitivity was 91.7%, and specificity was 83.9%. Conclusion: The use of enhanced CT to obtain ECV is helpful in predicting the pathologic grade of rectal cancer; however, this result has to be confirmed in a study with a larger sample size.